The present invention relates to physiological sensing, in particular to sensing and display of skin conductivity.
The skin-conductivity response, also known as the electrodermal response, is the phenomenon whereby the skin momentarily becomes a better conductor of electricity in response to external or internal stimuli that are physiologically arousing. In this context, the term xe2x80x9carousalxe2x80x9d broadly connotes overall activationxe2x80x94i.e., an increase in the intensity of general physiological activity. Arousal is widely considered one of the two main dimensions of an emotional response; the other, valence, represents the positive or negative quality of the response (so that winning an award is high arousal, positive valence whereas listening to a boring speech is low arousal, negative valence). Measuring arousal is therefore not the same as measuring emotion, but does capture an important component of it. Arousal has been found to be a strong predictor of attention and memory.
The stimuli to which skin conductivity is sensitive are manifold, including events of a novel, significant, or intense nature. Arousal level tends be low when a person is sleeping, and high in activated states such as rage or mental workload. Engaging in a task that imposes mental workload, such as solving math problems (even if not particularly difficult), will tend to cause skin conductivity to increase sharply and then gradually decline.
The skin-conductivity response is measured from the eccrine glands, which cover most of the body and are concentrated in the palms and the soles of the feet. The primary function of the eccrine glands is thermoregulation (by evaporative cooling of the body), which is related to aerobic activity. The eccrine glands located on the palmar and plantar surfaces, however, have been suggested to be more responsive to emotional and other significant stimuli. Emotion-evoked sweating, for example, is most evident in these areas due to the high gland density.
Conductivity is typically measured by placing two electrodes next to the skin and passing a minuscule electric current between the two points. When the subject experiences increased arousal, the skin immediately becomes a slightly better electrical conductor, and this response is detected by appropriate circuitry associated with the electrodes. Presently available devices, however, are elaborate and sophisticated, requiring specialized electrodes and gels, and are primarily intended for use in a laboratory setting. The measurement circuitry is ordinarily part of a stationary processing system.
The present invention provides a skin-conductivity sensor configured as a wearable device, preferably a glove (or, as shown in the figures, an article of clothing worn on the hand but covering it only partially). The device may include an on-board power source and processing hardware.
The design of the article is dictated, in part, by the locations of the conductivity-measuring electrodes. Electrodes in skin-conductivity sensors have traditionally been placed either on the middle phalanges of the digits (FIG. 1A) or on the bottom of the palmar surface of the hand (FIG. 1B). In accordance with the present invention, by contrast, a first electrode is held against the bottom of the palmar surface and a second electrode lies against the side of the hand, between the index finger and the thumb. This placement is particularly advantageous in facilitating configuration of a wearable skin-conductivity garment as a hand-worn article and in minimizing motion artifacts.